Parts of Rotorua, Whangarei and the Far North are among the most vulnerable in the country to increases in the cost of petrol.

The results are revealed in a study by Abley Transportation Consultants – commissioned by the Palmerston North City Council – to find out how New Zealand towns and cities will cope when oil becomes much more expensive.

"This study is unique because it takes the oil resource debate from a theoretical position, and applies engineering and economic analysis to forecast what might happen in a post cheap oil environment," lead author Steve Abley says.

"The dominant conclusion is New Zealand can still be prosperous in a post cheap oil world, but there is increasing risk if the commitment to reduce transport fuel demand is deferred."

While the report focuses mainly on Palmerston North, it also includes an assessment of 1748 New Zealand suburbs, ranking them by their vulnerability to mortgage, petrol and inflation risks.

The most vulnerable are Mamaku in Rotorua, Hikurangi in Whangarei and Awanui in the Far North.

Mamaku has a high vulnerability ranking because 74.1% of households have a mortgage, 81.6% of workers get to work by car and the median household income in 2006 was at least $39,600.

In comparison, in the least vulnerable suburb, Roseneath in Wellington, just 40.9% of households have a mortgage, 46.3% get to work using a car and the median household income is at least $100,000.

The other least vulnerable suburbs are Oriental Bay and Kelburn in Wellington, Ohakea in Manawatu and central Whangarei.

In Auckland, swanky Remuera West is ranked the 49th least vulnerable suburb nationwide, with 41.6% of households having a mortgage, 65.9% travelling to work by car and an average household income of more than $100,000.

Another Auckland suburb, Otahuhu West, is ranked 1626th, with 69.7% of households having a mortgage, 65.8% of workers using a car to get to work and an average household income of $40,100.